A wide variety of off-line LED drivers are known. For example, a capacitive drop off-line LED driver from On Semiconductor (Application Note AND8146/D) is a non-isolated driver with low efficiency, is limited to deliver relatively low power, and at most can deliver a constant current to the LED with no temperature compensation, no dimming arrangements, and no voltage or current protection for the LED.
Other isolated off-line LED drivers also have wide-ranging characteristics, such as a line frequency transformer and current regulator (On Semiconductor Application Note AND 8137/D); a current mode controller (On Semiconductor Application Note AND8136/D: a white LED luminary light control system (U.S. Pat. No. 6,441,558); LED driving circuitry with light intensity feedback to control output light intensity of an LED (U.S. Pat. No. 6,153,985); a non-linear light-emitting load current control (U.S. Pat. No. 6,400,102); a flyback as an LED Driver (U.S. Pat. No. 6,304,464); a power supply for an LED (U.S. Pat. No. 6,557,512); a voltage booster for enabling the power factor controller of a LED lamp upon a low AC or DC supply (U.S. Pat. No. 6,091,614); and an inductor based boost converter (e.g., LT 1932 from Linear Technology or NTC5006 from On-Semiconductor).
In general, these various LED drivers are overly complicated, such as using secondary side signals (feedback loops) which have to be coupled with the controller primary side across the isolation provided by one or more transformers. Many utilize a current mode regulator with a ramp compensation of a pulse width modulation (“PWM”) circuit. Such current mode regulators require relatively many functional circuits and while nonetheless continuing to exhibit stability problems when used in the continuous current mode with a duty cycle or ratio over fifty percent. Various prior art attempts to solve these problems utilized a constant off time boost converter or hysteric pulse train booster. While these prior art solutions addressed problems of instability, these hysteretic pulse train converters exhibit other difficulties, such as electromagnetic interference, inability to meet other electromagnetic compatibility requirements, and are comparatively inefficient. Other solutions, such as in U.S. Pat. No. 6,515,434 B1 and U.S. Pat. No. 6,747,420, provide solutions outside the original power converter stages, adding additional feedback and other circuits, which render the LED driver even larger and more complicated.
Accordingly, a need remains to a comparatively high efficiency, stable and electromagnetically compatible LED driver controller for high brightness applications. In addition, such a controller should be included within and provide a process and system for controlling a switching power converter, constructed and arranged for supplying power to one or plurality of LEDs to reduce the size and cost of LED driver. It also would be desirable for the controller to be stable independently and regardless of the current through LED. In addition, the controller should provide a high efficiency LED driver with a reliable protection for driver components and LEDs.